1. Field of the Invention
The present invention relates to a portable microscope for use in inspecting fiber optic connections, and more particularly, to a portable microscope with an end plate and adapter for inspecting an end of a fiber optic cable. The adapter of the portable microscope is movable to facilitate viewing of multiple fibers mounted in a single connector.
2. Summary of Related Art
Fiber optic systems have optical connections at each junction between a fiber optic cable and a light source or detector. Connections are also needed to join or splice together the ends of two cables. Since each fiber optic system will include a number of junctions of fiber optic cable, it is essential that the technicians working on fiber optic cables in the field use a microscope and other tools to properly connect the fiber optic cables.
In the installation of a fiber optic system, transmitters and receivers may be positioned throughout the system at the desired locations for transmitting and receiving signals. The transmitters and receivers are mounted in a light interface unit which includes both electrical receptacles for input/output of electrical signals and lighting receptacles for the input/output of light signals. After the light interface units with transmitters and receivers have been installed and the cable between the light interface units pulled, one of the final field steps to complete the installation is connectorization, which is the connection of fiber optic connectors to the ends of the fiber optic cables to facilitate the proper alignment of the core of the fiber optic cable at the fiber optic connections.
In a fiber optic system, a receptacle is a termination device for a fiber optic connection. The receptacle has two ports aligned with a center aperture to promote proper alignment of the fiber optic cable cores at the point of connection. In a light interface unit, the receptacle is mounted in a fixed position with one port connected to a transmitter or receiver and the second port aligned for the insertion of a connector on the end of the fiber optic cable. Receptacles are also used outside of the light interface units to splice together two fiber optic cables.
The fiber optic cables used in a system will have a connector secured to each end of the fiber optic cable, the connector being designed for insertion and locking in the receptacle. The cable is stored on spools and is pulled from the spools in the field during installation. Several different types of receptacles and connectors are available for use in fiber optic systems.
The connectors are typically installed on the fiber optic cable in the field at the time of installation. The fiber optic cable is stripped of its protective covering and the glass core and cladding are inserted into the connector such that the glass core extends from the ferrule at the end of the connector. The cable is epoxied into the connector and the glass core at the end of the ferrule is cleaved and polished using a lapping process.
The polished end of the core of the cable must be inspected to ensure that the end surface is clean and scratch free. Any scratches or cracks in the end of the glass fiber will adversely effect the integrity of the connection. Even body oils, lint or dust can cause unacceptable losses at the connection.
Because the glass core of a fiber optic cable is so small and because a good connection is essential to the overall efficiency of the system, a portable microscope for use in connecting the connectors to the fiber optic cable is an essential tool for the technician. The technician in the field must be able to inspect the end of the core of the fiber optic cable to ensure a smooth and clean surface for transmission of the light.
U.S. Pat. Nos. 5,731,893 and 5,982,533 are patents directed to portable microscopes and issued to the present inventor. These two patents contain additional background information and are incorporated herein by reference. Additional microscopes for inspection of fiber optic cables are disclosed in U.S. Pat. Nos. 4,505,556; 4,595,265; 4,640,578; 4,671,629; and 5,196,899.
Connectors with multiple fibers are now being used in the industry. The multi-fiber connectors permit several fibers in the same space as a standard connector. In a typical two-fiber connector, the fibers are 4.5 millimeters apart. Such spacing between the fibers makes it more difficult to inspect the fibers, since the connector must be repositioned to inspect the ends of both of the fibers. The technician must inspect all of the fiber ends in the connector, and it is difficult to conduct a field inspection of a multi-fiber connector using a microscope with a typical fixed endplate configuration.
Technicians have a need for a microscope endplate which facilitates the inspection of all the fiber ends of a multi-fiber connector. The endplate should include an adjustable head which permits each of the fiber ends to be positioned in the viewing range of the scope at the proper magnification for inspection. Once the block of the connector is positioned in the endplate of the microscope, it is desirable to inspect all of the fibers without removing the connector from the endplate.
A polishing puck may be used to polish the ends of the fiber optic cables in the connector. Technicians also need the capabilities of inspecting the ends of the fiber optic cable when secure to the polishing puck. The inspection and any additional polishing could be accomplished in a single puck mounting. Technicians would not have to remount the connector in the puck if further polishing was required after inspection.
A number of multi-fiber connectors are being used in the industry. The multi-fiber connectors currently include 2 to 12 fibers in each connector. Lucent Corporation manufactures an LC connector, which is a two fiber connector about one-half the size of a normal SC connector. Siecor and others provide a connector, such as the MT-RJ, which also includes 2 fibers in a single connector. The MTP connector by Siecor Corporation is used with a 12 fiber ribbon. The Volition VF-45, SG series of connectors is built by 3M Company and includes multiple fibers. In general, the spacing between the two fibers of a two-fiber connector is 4.5 millimeters.
In accordance with the present invention, there is provided a portable microscope with an adjustable end plate for improved inspection of the end surface of multiple fiber optic cables mounted in a single connector. The hand held microscope used for field inspection of fiber optic surfaces at connection points typically includes 100xc3x97 magnification capabilities and a battery powered light source. Hand held microscopes with 200xc3x97 and greater magnification are also available for field use.
The end plate of the hand held microscope of the present invention is mounted on the head unit housing of the microscope and includes a movable adapter or fixture for receiving and adjustably positioning a connector with multiple fiber optic cables. The adapter includes a jig formed on one side to retain and position the connector for viewing of the ends of the fiber optic cables.
Because the microscope can only focus on one end of a fiber optic cable at a time, and because the cables are spaced apart, it is necessary to move reposition the connector to view all of the fiber optic cables. Once the connector is mounted in the adapter of the present invention, the position of the connector may be adjusted by pivoting the adapter on the end plate to facilitate inspection of all of the fiber optic cables in the connector.
The end plate of the hand held microscope may also be formed of a flat surface to engage the face of a polishing puck with the connector secured to the puck. The ends of the fiber optic cables are generally co-planar with the surface of the puck. The end plate includes a support flange such that the flange engages the edge of the puck and facilitates the positioning of the ends of the fiber optic cable for viewing.
For the movable adapters, the end plate includes a common base plate secured to head unit housing, and a post or other means for pivotably securing the adapter to the end plate. The adapter is a fixture having a jig formed for receiving and positioning the connector. The adapter is pivotably connected to the end plate such that all of the fibers in a multi-fiber adapter can be inspected by pivoting (rotating) the adapter on the end plate.
The end plate is secured to the end surface of the head unit housing. The head unit housing includes three apertures, a large aperture at one side for viewing purposes, a center aperture for securing the end plate, and an aperture for receiving a stabilizer bar or pin extending from the end plate. A flat head screw is used to secure the end plate to the head unit housing. The stabilizer bar is important in preventing the end plate from rotating about the screw.
The outer surface of the end plate includes a cylindrical extension, which is used to pivotably secure one end of the adapter to the end plate. The bottom surface of the adapter includes an aperture, which is positioned about the flat head screw used to secure the end plate. When the adapter is pivoted about the extension, the flat head screw engages the edge of the aperture in the adapter and acts as a stop to limit the range of rotation. Since the ends of the fiber optic cable mounted in the adapter are in close proximity, the adapter only requires a small degree of movement to permit inspection viewing of the ends of the fiber optic cables.
The end of the adapter adjacent the viewing aperture of the end of the head unit housing is formed to receive and position the connector for viewing the ends of the fiber optic cable. The connector is retained in the adapter and the adapter is pivoted about the end plate so that every one of the fiber optic cables can be inspected.
Since each of the main connectors used in the industry has a different external configuration, a single adapter will not accommodate all of the connectors. In the present invention, a common end plate can be used with various adapter configurations. The jig formed on one side of the adapter is changed for each of the embodiments of the adapter. Because only a single screw is used to retain the adapter to the cylindrical extension of the end plate, a technician can easily change from one adapter to another when encountering different connectors.
The present invention provides a portable microscope with improved fiber optic cable inspection capabilities for multiple fiber connectors. By pivoting the adapter on the end plate, all of the fiber ends in a multi-fiber connector can be inspected in quick and convenient manner.
The present invention also provides adapters having jigs design to receive and retain connectors such that the ends of the fiber optic cables in the connectors are in the desired position for inspection. For the technician who works on a variety of multi-fiber connectors, the different adapters may be changed by a single screw connection to the end plate.
The head unit housing contains mounting holes for securing the end plate to the housing at the end of the microscope. The hole configuration may also be used to mount other end plates as disclosed in applicants earlier patents, U.S. Pat. Nos. 5,731,893 and 5,982,533. By maintaining the same hole configurations in the housing, a single microscope can accommodate a variety of single fiber and multi-fiber end plates.
The present invention also includes an alternative embodiment of an end plate, which is used for viewing the fiber optic cables in a connector mounted in a polishing puck. The end plate includes a retention flange or ridge which assists in positioning the ends of the fiber optic cables in position for viewing. The technician may inspect the ends of the cables and then immediately resume the polishing process if the inspection indicates that further polishing is required.